Vehicle drive system and control means therefor

ABSTRACT

A hydraulic drive system for motor vehicles, particularly track vehicles, of the type having hydraulic motors for each of the tracks and pumps for each of said motors, with each pump being driven by a prime mover. The output of each pump is inversely proportional to the pressure of a fluid control signal fed back from the output line of the pumps through a pressure regulator which regulates the pressure of the control signal. A governorregulator communicates with the first-mentioned regulators and sets the lower limit of the pressure range of the control signal and thereby sets the upper limit on the speed of the vehicle because of the inverse relationship between the output of the pumps and the pressure of the control signals.

United States Patent 1191 Roe et al.

[54] VEHICLE DRIVE SYSTEM AND CONTROL MEANS THEREFOR [75] Inventors:Robert A. Roe; Gerald C. Anderson,

both of Oconomowoc, Wis.

[73] Assignee: Applied Power Industries, Inc., Milwaukee, Wis.

22 Filed: July 17,1970

211 App]. No.: 55,729

1 51 Feb. 20, 1973 Primary Examiner-Benjamin Hersh AssistantExaminer.lohn A. Pekar Attorney-John J. Bryne ABSTRACT A hydraulic drivesystem for motor vehicles, particularly track vehicles, of the typehaving hydraulic motors for each of the tracks and pumps for each ofsaid motors, with each pump being driven by a prime mover. The output ofeach pump is inversely propor- [52] US. Cl. ..180/6.48, 180/66 R tionalto the pressure ofa fluid control signal fed back lift- Cl. from theoutput line of the p p through a pressure Fleld of search-"180M481 66 R;60/52 VS regulator which regulates the pressure of the control signal. Agovernor-regulator communicates with the [56] References C edfirst-mentioned regulators and sets the lower limit of the pressurerange of the control signal and thereby UNITED STATES PATENTS sets theupper limit on the speed of the vehicle 3.224.196 12/1965 Bennett..180/6.48 x because of the inverse relationship between h Output3.233.691 2/1966 Dc 131661 ..180/6.48 0f the P p and the D 0f thecontrol 81811818- FOREIGN PATENTS OR APPLICATIONS 4 Claims, 2 DrawingFigures 979,453 1/1965 Great Britain ..l80/6.48

MOTOR PATENTED FEHZO I975 sum 1 OF M/VE/VTORS ROBERT A. ROE 6ER4LD O.ANDERSON A OR/VEY PATENTEH FEB 2 01973 SHEET 2 OF /NV/VTO/?$ ROBERT A.ROE GERALD a. ANDERSON A TOR/V5) 6 mm mm 102 50% 25 3 mozfi ow i766 i528VEHICLE DRIVE SYSTEM AND CONTROL MEANS THEREFOR This invention relatesto a hydraulic drive system for a vehicle and more particularly to meansfor controlling the drive system and limiting the speed of the vehicle.

The system of this invention is particularly adapted for use in endlesstrack vehicles wherein the respective tracks are driven at differentrelative speeds in steering the vehicle. Generally, the turning of atrack vehicle is accomplished by braking one track relative to the otherthrough systems employing a brake pedal for each track. The maintenanceexpense involved in replacing worn brakes is obviously quite high not tomention the inefficient use of the power means which is working againstthe brakes in the turning operation.

It is an object of this invention to provide a simple and efficientmeans for controlling the turning movements of track vehicles.

It is another object of this invention to provide a hydraulic governorfor track vehicles or other lowspeed vehicles.

It is a further object of this invention to provide a sensitive andaccurate, yet durable, hydraulic pressure regulator control system foruse in drive systems employing hydraulic motors driven by a pump whoseoutput is inversely proportional to the pressure of a control signal fedback from said pump output through said regulator system. A pump of thetype referred to above wherein the output of the pump is inverselyproportional to the pressure of a control signal is disclosed inassignees copending application by Hamish Cattanach, Ser. No. 738,050,filed June 18, 1968, entitled: Variable Pressure Sensitive Pump, nowabandoned, which is a continuation-in-part of Ser. No. 660,505, filedAug. 14, 1967, entitled: Variable Pressure Sensitive Pump, nowabandoned.

The pump is an axial piston pump having by-pass valves in the cylindersthereof, which valves are normally in the closed position. When in theclosed position, the output of the pump is at maximum for a given rotaryspeed of the pump. A hydraulic pressure source, preferably a feedback ofa portion of the pump output, is used to control the open period of theby-pass valves in each cylinder during a portion of the piston stroke,bleeding off some of the fluid in the cylinder to tank thereby reducingthe output of the individual cylinders and the pump as a whole. Thepressure of the feed-back signal determines the duration of the openperiod of the by-pass valve. The duration of the open period variesdirectly proportaionally with a change in pressure.

The pressure regulators of this invention can be hydraulically adjustedto maintain the pressure level of the control signal at a selectedminimum level thereby limiting the maximum output of the pumps andthereby the speed of the hydraulic motors because of the inverserelationship of pump output and control signal pressure.

More specifically, this invention comprises a drive system for a vehiclehaving right and left ground-engaging means, comprising, first andsecond hydraulic motors driving the ground-engaging means respectively,a pump for each of said motors of the type having a variable outputwhich is inversely proportional to a control signal fed to said pumps.First and second pressure regulator means to regulate the pressure ofthe control signal to said first and second pumps respectively over arange of pressures. Manual actuators are employed for said first andsecond regulators. A third regulator communicates with each of the firstand second regulators for selectively setting the lower limit of saidpressure range regulated by said first and second regulatorsirrespective of the manual actuators. The first and second regulatorsare interposed between the output and control signal input of each pumprespectively and comprise spring-biased check valves which normallyclose off communication to the control signal input because the outputpressure which acts on the valve is greater than the pre-set biasingforce. Upon depressing a manual actuator the biasing force is increasedand the valve will open transmitting a portion of the output pressure tothe pump thereby increasing the pressure of the control signal,decreasing the output of the pump and slowing down the motor. For agiven biasing pressure, the valve will modulate to maintain the propercontrol signal pressure. The third regulator, which is identical to thefirst and second regulator also communicates with the output of eachpump. It also has an actuator which increases the biasing force on itsvalve. When the actuator of the third regulator is set at a certainposition, a certain portion of the output of the pump will betransmitted to the first and second regulator to augment the biasingforce in each of said regulators against the output pressurescommunicated to each of said regulators. ln this manner a certaincontrol signal pressure somewhere above zero will be maintained throughthe regulators thereby limiting the output of the pumps, irrespective ofthe manual actuators for the first and second regulators.

These and other objects of the invention will become more apparent tothose skilled in the art by reference to the following detaileddescription when viewed in light of the accompanying drawings wherein:

FIG. 1 is a partially diagrammatic showing of the system of thisinvention; and

FIG. 2 is an enlargement of one of the pressure regulators shown in FIG.1.

Referring now to the drawing wherein like numerals indicate like parts,the drive system of this invention is shown diagrammatically in FIG. 1.The system as shown and as will be described, is for a vehicle,particularly a track vehicle, wherein the ground-engaging means of thevehicle are separately driven and controlled. The system is particularlyuseful in effecting the turning movement of endless track vehicleswherein the speed of one track is varied relative to the other.Hydraulic motors l0 and 12 are employed for right and left wheels ortracks respectively. Any conventional hydraulic motor can be usedalthough rotary motors of the axial piston-cylinder variety arepreferred. Communicating with and driving each of the motors 10 and 12are pumps 14 and 16, respectively, of the type referred to earlier anddisclosed in assignees copending application by Hamish Cattanach, Ser.No. 738,050, filed June 18, 1968, entitled: Variable Pressure SensitivePump which is a continuation-in-part of Serial No. 660,505, filed Aug.14, 1967, entitled: Variable Pressure Sensitive Pump, now abandoned.

The output lines of the pumps 14 and 16 are indicated by the numerals 18and 20 respectively and the control signal lines to the pumps areindicated by the numerals 22 and 24. As mentioned earlier the output ofthe pumps and consequently the pressures in lines 18 and 20 varyinversely with the pressure in control signal lines 22 and 24.

The control signal consists of fluid feed-back from the pump outputlines 18 and 20 through feed back lines 26 and 28. The feed-back linescommunicate the output pressure to a first pressure regulator 30, asecond pressure regulator 32 and a third pressure regulator 34 viatake-off lines 36, 38 and 40 respectively. The control signal isprovided by the outputs of the pumps as regulated by regulators 30 and32. Each of the regulators are provided with manual actuators 42, 44 and46, and in the case of a track vehicle or the like the actuators ofregulators 30 and 32 are in the form of foot pedals which independentlycontrol the speed of the tracks relative to each other as will befurther described. The regulators 30 and 32 are preset such that theynormally communicate the pump output pressure to tank therebymaintaining the control signal pressure substantially at zero. Upondepression of actuator 42 or 44, a certain portion of the outputpressure is transmitted through the regulators 30 or 32 through thecontrol signal lines 22 and 24. With the rise in the pressure of thecontrol signal a corresponding decrease in output occurs in accordancewith the particular setting of the actuator. Thereby the speed of motorand consequently its driven track will decrease. If only one actuator isdepressed, then one track will be driven at a lower speed than the otherthereby effective a turning movement.

When the actuators are in the non-actuated position, the vehicle cantravel at full speed. Full speed is determined by the speed of a primemover not shown, which drives the pumps 14 and 16. It is to beunderstood that a separate throttle can be used to control the speed of"the prime mover.

The third regulator whose operation is substantially identical to thatof the first and second regulators communicates with those regulatorsthrough lines 48, 50 and 52. When its actuator 46 is depressed, such asby a hand lever, the pressure in lines 42 and 44 rises, and as will bediscussed below, has the same effect on the regulators 30 and 32 as doesthe actuation of the actuators 42 and 44. The result is that a minimumlevel of pressure is maintained in control signal lines 22 and 24 andthereby a maximum level of output and vehicle speed, somewhere belowfull throttle, is maintained.

I will refer now to the particular structure and operation of theregulator and since the regulators are identical, only one, 32, will bedescribed. Referring to FIG. 2, the regulator 32 comprises a housing 54having centrally disposed bores 56 and 60 communicated by intermediatebore 58. The housing is sealed at each end by plugs 61 and 62. Theactuator comprises a reciprocating piston 64 and rod 66, the latter ofwhich extends through plug 62. Seals 68 and 70 prevent leakage about therod 66, and, as mentioned earlier a foot pedal can be attached to theouter end of the rod 66 when used in track vehicle driving systems, forexample. The piston 64 is slidably received in bore 60 and is normallymaintained in the position shown by spring 72. Slidably mounted inintermediate bore 58 is cylindrical valve 74 having an annular groove 76forming a chamber with the walls of the bore 58 and having an axiallyextending passageway 78 terminating at one end in opening 80 and at theother end in radially outwardly extending ports which in turn terminatein annular groove 84.

The regulator housing has a first port 84 communicating with the outputpressure feed back line 38, and terminating in the annular chamberdefined by the an nular groove 76 in valve 74. A second port 86communicates the chamber 56 with the control signal line leading to thepump and a third port 88 communicates the bore 60 with the third port ofthe third regulator or governor 34. In the third regulator 34 thecorresponding first port is connected to the output line pressure as arethe first ports of the other regulators. The corresponding second portcommunicates with the third port of each of the other regulators and thecorresponding third port of the third regulator communicates with thetank or reservoir which is at zero pressure.

As mentioned above, the valve 74 is normally maintained in the positionshown in FIG. 2 by spring 72 and disc 90, the latter of which abutsagainst the valve 74 via rounded bearing surface and bearing recess 92and 94 respectively. When the pump is actuated, a portion of the outputis taken off by the feedback line 28 through check valve 96. Pressure istransmitted through the first port 84 and into the annular chamber orgroove 76. The pressures impinge against the surfaces 98 and if greaterthan the biasing force of the spring 72, forces the valve to the rightagainst the biasing force of the spring. The spring biasing force ineach regulator will normally be set such that the output pressure uponoperation of the pump will cause the valve to move to the right wherebythe rear end wall 100 of the annular groove 76 overlaps with the rearportion 102 of the bore 56 to close off communication between groove 76and bore 56. In this position, the second port 86 is communicated withthe third port 88 via bore 56, passageway 78 and radial passageways 82.Since all of the regulators are communicated to the same outputpressure, absent any actuation of the actuators, each of the regulatorvalves will be in the same position. Consequently, the second and thirdports in the third regulator 34 also will be in communication with eachother, thereby the control signal lines will be communicating with tankwhich is at zero pressure meaning the output of the pumps will bemaximum.

The valve 74 is biased to the left-most position by the spring 72, asshown in the drawings, whereby the first port 84 is in communicationwith the second port 86. However, as mentioned above, when the pressurefrom the output line reaches a certain value, it overcomes the action ofthe spring 72 closing off the communication between port 84 and port 86.By depressing the actuator 66, however, the biasing force of the spring72 can be progressively increased whereupon greater pressure will berequired to move the valve to the right position, which in turn meansthat the first port will be in communication with the second port agreater period of time, thereby increasing the pressure of the controlsignal and decreasing the output of the pump. It is to be understoodthat any particular setting of the actuator, the valve will continue tomodulate by reciprocating back and forth maintaining the desiredpressure in the control signal line.

The purpose of the third actuator is to act as a governor to set a lowerlimit on the pressure which is transmitted through the control signallines to the pumps thereby setting a maximum limit on the output of thepumps and a maximum limit on the speed of the motors. This isaccomplished by depressing the actuator 46 of the regulator 34. In sodoing, the first and second ports 91 and 93, of the third actuator willbe in communication and output pressure will be transmitted to the thirdports of the first and second regulators at a level depending on thedegree of actuation of the actuator 46. The increase in pressure will betransmitted through lines 48, 52 and 50 raising the pressure of thefirst and second regulators irrespective of their actuators 42 and 44.For example, the actuator 46 may be set at one position and maintainedthere and in so doing, a certain pressure over and above the pressureset by the spring will be maintained in chamber 56 in each of theregulators 30 and 32. It is to be understood that under normal springbiasing action, when the actuator of each regulator is at its fullnon-actuating position, the pressure at 84 is communicative withpressure at 88 through passage 78 of valve 74 since the output pressureat 84 is sufficient to overcome the spring force and to drive the valveto the' right. But upon increase in pressure driving valve 74 to theleft, the pressure in the control signal lines will raiseproportionally. Once the third regulator-governor has been set at acertain level, any additional pressure supplied by a depression of theactuators of the two regulators will serve to increase the pressuresover and above the minimum pressures set in by the governor.

In operation, a prime mover, not shown, drives pump 14 and pump 16 at apredetermined speed. At this predetermined speed, the output of eachpump will be maximum when each of the actuators 42, 44 and 46 of theregulators 30, 32 and 34 are in the non-actuated position. Uponactuation of each of the actuators 42 and 44 either separately orsimultaneously a portion of the pump output pressure will be transmittedback to the pump by an output regulating control signal. As mentionedearlier, the pump output is inversely proportional to the pressure ofthe control signal. In the nonactuated position of the actuators 42, 44and 46, the control signal pressure is zero and pump output is maximumfor a given speed of the primer mover driving the pumps and, therefore,vehicle speed is maximum. The maximum speed of the vehicle can belowered or governed, however, by actuating the actuator 46 ofregulator-governor 34. By so doing, a portion of the pump outputpressure is transmitted to each of the regulators 30 and 32 to increasethe pressure acting on the valve 74 irrespective of the actuation of theactuators 42 and 44. This in turn increases the control signal pressurefrom zero upward to a level corresponding to the degree of adjustment ofthe regulator 34. Consequently, because of the above-mentioned inverserelationship, the maximum level of pump output and consequently themaximum motor speed will be lowered. The actuators 42 and 44 still areused, but any biasing force applied by those actuators will be inaddition to that set in by the regulator 34.

The system as shown particularly adapted for the operation of trackvehicles where it is desirable to slow down one track relative to theother to effect a turning movement. However, it is to be understood thatthis system can be used for any wheeled vehicle whether the movement ofthe wheels is controlled independently or in unison. For example, thefirst and second regulators could be connected to one actuation sourcesuch that both wheels of the vehicle are controlled simultaneously byone actuator movement.

In a general manner, while there has been disclosed an effective andefficient embodiment of the invention, it should be well understood thatthe invention is not limited to such an embodiment as there might bechanges made in the arrangement, dispoition, and form of the partswithout departing from the principle of the present invention ascomprehended within the scope of the accompanying claims.

We claim:

1. In a vehicle having right and left ground-engaging means, a drivesystem comprising first and second hydraulic motors for driving saidright and left groundengaging means respectively, a pump for drivingeach of said hydraulic motors of the type having a variable outputinversely proportional to the pressure of a hydraulic control signal,the improvement comprising, first and second pressure regulator meansregulating the pressure of the control signal to said first and secondpumps respectively over a range of pressures, actuators for said firstand second pressure regulators, a third regulator communicating witheach of said first and second regulators, said first and secondregulators being in communication with the output pressure of said pumpsand variably communicating said output pressures back to said first andsecond pumps over said range of pressures as said control signals, saidthird regulator being in communication with the output pressure of saidpumps and variably communicating a portion of said output pressure tosaid first and second regulators for assisting in the control of saidfirst and second regulators and for setting a lower limit of saidpressure range of said control signal irrespective of said actuators.

2. In a vehicle, a drive system comprising a hydraulic drive motor, apump for driving said motor of the type having a variable output whichis inversely proportional to the pressure of a hydraulic control signal,the improvement comprising, first pressure regulator means regulatingthe pressure of the control signal to said pump over a range ofpressures, actuator means for controlling said pressure regulator meansand thereby controlling the pressure of said control signal, secondpressure regulator means communicating with said first regulator means,each of said regulators being in communication with the output pressureof said pump, said first regulator variably communicating said outputpressure back to said pump as said control signal over said range ofpressures, said second regulator means variably communicating saidoutput pressure to said first regulator means to assist in the controlthereof and selectively setting a lower limit of said pressure rangeregulated by said first regulator means irrespective of said actuatormeans.

3. In a vehicle having right and left ground-engaging means, a drivesystem comprising first and second hydraulic motors for driving saidright and left groundengaging means respectively, a pump for drivingeach of said hydraulic motors of the type having a variable outputinversely proportional to the pressure of a hydraulic control signal,the improvement comprising, first and second pressure regulator meansregulating the pressure of the control signal to said first and secondpumps respectively over a range of pressures, actuators for said firstand second pressure regulators, a third regulator communicating witheach of said first and second regulators, means communicating the outputpressures of said pumps to each of said regulators, siad first andsecond regulators variably communicating the output pressure back tosaid first and second pumps as control signals, valve means in eachofsaid regulators responsive to said output pressures, adjustable biasingmeans operated by said actuators acting on said valve means whereby thegreater the biasing force the greater the pressure transmitted from theregulators as control signals, said third regulator variablycommunicating said output pressure to said first and second regulatorswhereby the force of the biasing means of the first and secondregulators is augmented by the pressure transmitted from said thirdregulator thereby providing a minimum biasing force irrespective of saidadjustable biasing means and setting a lower limit on the pressurestransmitted as control signals.

4. A vehicle drive system as defined in claim 3 wherein each of saidregulators are substantially identical and each have first, second andthird ports, said first port is in communication with said output linesof said pumps, and in said first and second regulators, said second portis in communication with the pressure responsive control means of eachof said pumps said third port is in communication with the second portof said third regulator, said third port of said third regulatorcommunicating with tank, and each of said valves have first and secondpositions, first passageway means communicating said first port withsaid second port when said valve is in said first position, secondpassageway means communicating said second port with said third port,when said valve means is in said second position, said valves urged tosaid first position by said biasing means and movable to said secondposition in response to pressure from said output lines in excess of theforce exerted by said biasing means, said valve normally assuming saidsecond position absent actuation of the actuator and augmentation of thebiasing force by the third regulator.

1. In a vehicle having right and left ground-engaging means, a drivesystem comprising first and second hydraulic motors for driving saidright and left ground-engaging means respectively, a pump for drivingeach of said hydraulic motors of the type having a variable outputinversely proportional to the pressure of a hydraulic control signal,the improvement comprising, first and second pressure regulator meansregulating the pressure of the control signal to said first and secondpumps respectively over a range of pressures, actuators for said firstand second pressure regulators, a third regulator communicating witheach of said first and second regulators, said first and secondregulators being in communication with the output pressure of said pumpsand variably communicating said output pressures back to said first andsecond pumps over said range of pressures as said control signals, saidthird regulator being in communication with the output pressure of saidpumps and variably communicating a portion of said output pressure tosaid first and second regulators for assisting in the control of saidfirst and second regulators and for setting a lower limit of saidpressure range of said control signal irrespective of said actuators. 1.In a vehicle having right and left ground-engaging means, a drive systemcomprising first and second hydraulic motors for driving said right andleft ground-engaging means respectively, a pump for driving each of saidhydraulic motors of the type having a variable output inverselyproportional to the pressure of a hydraulic control signal, theimprovement comprising, first and second pressure regulator meansregulating the pressure of the control signal to said first and secondpumps respectively over a range of pressures, actuators for said firstand second pressure regulators, a third regulator communicating witheach of said first and second regulators, said first and secondregulators being in communication with the output pressure of said pumpsand variably communicating said output pressures back to said first andsecond pumps over said range of pressures as said control signals, saidthird regulator being in communication with the output pressure of saidpumps and variably communicating a portion of said output pressure tosaid first and second regulators for assisting in the control of saidfirst and second regulators and for setting a lower limit of saidpressure range of said control signal irrespective of said actuators. 2.In a vehicle, a drive system comprising a hydraulic drive motor, a pumpfor driving said motor of the type having a variable output which isinversely proportional to the pressure of a hydraulic control signal,the improvement comprising, first pressure regulator means regulatingthe pressure of the control signal to said pump over a range ofpressures, actuator means for controlling said pressure regulator meansand thereby controlling the pressure of said control signal, secondpressure regulator means communicating with said first regulator means,each of said regulators being in communication with the output pressureof said pump, said first regulator variably communicating said outputpressure back to said pump as said control signal over said range ofpressures, said second regulator means variably communicating saidoutput pressure to said first regulator means to assist in the controlthereof and selectively setting a lower limit of said pressure rangeregulated by said first regulator means irrespective of said actuatormeans.
 3. In a vehicle having right and left ground-engaging means, adrive system comprising first and second hydraulic motors for drivingsaid right and left ground-engaging means respectively, a pump fordriving each of said hydraulic motors of the type having a variableoutput inversely proportional to the pressure of a hydraulic controlsignal, the improvement comprising, first and second pressure regulatormeans regulating the pressure of the control signal to said first andsecond pumps respectively over a range of pressures, actuators for saidfirst and second pressure regulators, a third regulator communicatingwith each of said first and second regulators, means communicating theoutput pressures of said pumps to each of said regulators, siad firstand second regulators variably communicating the output pressure back tosaid first and second pumps as control signals, valve means in each ofsaid regulators responsive to said output pressures, adjustable biasingmeans operated by said actuators acting on said valve means whereby thegreater the biasing force the greater the pressure transmitted from theregulators as control signals, said third regulator variablycommunicating said output pressure to said first and second regulatorswhereby the force of the biasing means of the first and secondregulators is augmented by the pressure transmitted from said thirdregulator thereby providing a minimum biasing force irrespective of saidadjustable biasing means and setting a lower limit on the pressurestransmitted as control signals.